1. Field of the Invention
The invention relates to a display panel, and more particularly to, a liquid crystal display panel.
2. Description of Related Art
In 1888 A.D., Friedrich Reinitzer placed a cholesteric benzoate in a polarizing microscope and observed that the cholesteric benzoate would appear in different colors (blue-violet and blue) as in phases of isotropic and cholesteric, and a color variation phenomenon between the isotropic and cholesteric phases is only existed in a very small temperature interval (about a temperature interval of 1° C.). In 1970 A.D., many scientists confirmed the above-mentioned phenomenon is a new thermodynamically stable phase using methods, such as volumetric analysis, high resolution differential scanning calorimetry and so forth.
General liquid crystal is optically anisotropic, but the blue phase liquid crystal is, instead, optically isotropic. In other words, the blue phase liquid crystal has a very low or even does not have a birefringence. Nevertheless, since the periodic lattice of the blue phase is a function of visible light wavelength, a selective bragg reflection would occur. This feature enables the blue phase liquid crystal to be applied in the use of light modulators with a rapid response rate. However, regardless in terms of a theoretical prediction or an experimental observation, the blue phase liquid crystal only appears in molecular materials possessing high purity and high chirality, causing the blue phase liquid crystal to only exist within a very small temperature interval (a temperature interval smaller than 2° C.). Therefore, a practical application of the blue phase liquid crystal is rather difficult.
In recent decade, in order to enable the display quality of the liquid crystal display panel to override the quality of the cathode ray tube display, the blue phase liquid crystal with a rapid response characteristic is further subjected to academic and industry attentions. For the application need, the blue phase liquid crystal must possess a wide temperature application range; and therefore, different technical developments have successively been provided. For example, the polymer having a stable characteristic (producing polymer reticular structure) is being used to produce a blue phase which can exist within a wide temperature interval (Nature materials, 2002, 1, 64). In addition, in 2002 A.D., Kikuchi et al. successfully produced a blue phase with a temperature interval of 60° C. by adding a small amount of monomer and photoresist into the blue phase liquid crystal, and illuminating the mixture in the temperature range of the blue phase so as to produce a gel structure like stable blue phase.
Generally, the positive blue phase liquid crystal molecules are driven by a transverse electric field generated by an electrode design of in-plane switch mode (IPS), so that the positive blue phase liquid crystal molecules are formed as ellipsoids with birefringence. Under a circumstance without applying the electric field thereto, the positive blue phase liquid crystal molecules are optically isotropic. Under a circumstance of applying the electric field thereto, the positive blue phase liquid crystal molecules are optically anisotropic. Accordingly, when the display having the positive blue phase liquid crystal molecules is designed as a normally black type, the display would present in a bright screen under the circumstance of applying the electric field to the positive blue phase liquid crystal molecules and present in a black state under the circumstance without applying the electric field to the positive blue phase liquid crystal molecules. However, the electrodes with a coplanar design, e.g. the IPS-mode design, usually are the comb-like electrodes with a fixed pitch, no transverse electric field is existed above the electrode, so that the positive blue phase liquid crystal molecules right above the electrode are not driven by the transverse electric field to present the optically isotropic characteristic, thus having low transmittance and causing dark lines in the screen, such that the display quality of the liquid crystal display panel is negatively affected. In addition, the positive blue phase liquid crystal molecules in the literatures are displayed with a driving voltage, for example, as high as about 35 volts, and thus are harmful to a chip design of a driver circuit.